How to use a pipeline parameter containing spaces in Condition?

[haudren]

What happened:
I am using a pipeline parameter, and would like to use a Condition to switch on it existing / not existing. The condition I used is of the form parameter != '""'. When the parameter contains spaces (say parameter = "a b c"), it fails with:

This step is in Error state with this message: Invalid 'when' expression 'a b c != ""': Cannot transition token types from VARIABLE [a] to VARIABLE [b]

Another attempt with a, b, c results in:

This step is in Error state with this message: Expected boolean evaluation for 'a, b, c  != ""'. Got [a b true]

A quick look at the generated yaml shows that the parameter is compared unquoted which means that comparing it to a single string breaks...

What did you expect to happen:
I expect one of two things:

• There is a simple way to check for a single parameter to be set / not set that does not depend on the input containing strings
• There is a way to sanitize (quote) the input parameters before comparison

What steps did you take:
The pseudo-code:

import kfp.dsl as dsl
import kfp.components as comp
import os


def hello():
    print("Hello World")


hello_op = comp.func_to_container_op(hello)


@dsl.pipeline()
def my_pipeline(parameter="a b c"):
    with dsl.Condition(parameter == '!"'):
        hello_op()


if __name__ == "__main__":
    import kfp.compiler as compiler

    compiler.Compiler().compile(my_pipeline, os.path.splitext(__file__)[0] + ".yaml")

Anything else you would like to add:
I think this might be related to #1933 as this parameter is for all intents and purposes a list that I then pass to a shell script. I don't mind doing bits of parsing myself for the time being, but I'd like to not have the pipeline crash when spaces are passed in.

[Ark-kun]

This seems to be a quoting issue. I can try to fix it on our side, but it might be a bug in Argo.

[Ark-kun]

Does it work when your constant string is simple?
with dsl.Condition(parameter == 'abc'):

[haudren]

No, it seems like for most purposes, the value is interpreted literally. Stopgap fix I used is to replace spaces with underscores (most other separators won't work, as -/%& are numerical operators, ,;: are also argo operators).

I think this problem is related to the more general problem of having typed parameters in Kubeflow but for the moment, quoting predicate operators should be a good fix!